Recent years have seen a development of liquid crystal panel display apparatuses that adopt an RGBW display method. While a pixel is conventionally formed by three sub-pixels red (R), green (G), and blue (B), a pixel according to the RGBW display method is formed by four sub-pixels red (R), green (G), blue (B), and white (W). In this way, it is possible to decrease the luminance of a backlight that illuminates a liquid crystal panel from behind or the like by the amount of improvement of the luminance of each sub-pixel W. As a result, it is possible to reduce the overall power consumption of the display apparatus.
However, such display method could deteriorate the image quality, depending on control of the luminance of the backlight. Thus, techniques for solving this problem have been proposed. One technique uses a conversion table including luminance setting values that are set to achieve luminance suitable for an image signal. The luminance setting values are converted into backlight control values, which are supplied to the backlight.
According to another technique, an adjustment value for adjusting the backlight luminance is calculated from an average image luminance per screen and a luminance adjustment line. The backlight luminance is controlled by generating a signal for driving the backlight on the basis of the adjustment value. For the background art, see, for example, the following documents:
Japanese Laid-open Patent Publication No. 2007-322881
Japanese Laid-open Patent Publication No. 2010-002876